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      SUBROUTINE <a name="DSTEDC.1"></a><a href="dstedc.f.html#DSTEDC.1">DSTEDC</a>( COMPZ, N, D, E, Z, LDZ, WORK, LWORK, IWORK,
     $                   LIWORK, INFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  -- LAPACK driver routine (version 3.1) --
</span><span class="comment">*</span><span class="comment">     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
</span><span class="comment">*</span><span class="comment">     November 2006
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     .. Scalar Arguments ..
</span>      CHARACTER          COMPZ
      INTEGER            INFO, LDZ, LIWORK, LWORK, N
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Array Arguments ..
</span>      INTEGER            IWORK( * )
      DOUBLE PRECISION   D( * ), E( * ), WORK( * ), Z( LDZ, * )
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Purpose
</span><span class="comment">*</span><span class="comment">  =======
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  <a name="DSTEDC.20"></a><a href="dstedc.f.html#DSTEDC.1">DSTEDC</a> computes all eigenvalues and, optionally, eigenvectors of a
</span><span class="comment">*</span><span class="comment">  symmetric tridiagonal matrix using the divide and conquer method.
</span><span class="comment">*</span><span class="comment">  The eigenvectors of a full or band real symmetric matrix can also be
</span><span class="comment">*</span><span class="comment">  found if <a name="DSYTRD.23"></a><a href="dsytrd.f.html#DSYTRD.1">DSYTRD</a> or <a name="DSPTRD.23"></a><a href="dsptrd.f.html#DSPTRD.1">DSPTRD</a> or <a name="DSBTRD.23"></a><a href="dsbtrd.f.html#DSBTRD.1">DSBTRD</a> has been used to reduce this
</span><span class="comment">*</span><span class="comment">  matrix to tridiagonal form.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  This code makes very mild assumptions about floating point
</span><span class="comment">*</span><span class="comment">  arithmetic. It will work on machines with a guard digit in
</span><span class="comment">*</span><span class="comment">  add/subtract, or on those binary machines without guard digits
</span><span class="comment">*</span><span class="comment">  which subtract like the Cray X-MP, Cray Y-MP, Cray C-90, or Cray-2.
</span><span class="comment">*</span><span class="comment">  It could conceivably fail on hexadecimal or decimal machines
</span><span class="comment">*</span><span class="comment">  without guard digits, but we know of none.  See <a name="DLAED3.31"></a><a href="dlaed3.f.html#DLAED3.1">DLAED3</a> for details.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Arguments
</span><span class="comment">*</span><span class="comment">  =========
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  COMPZ   (input) CHARACTER*1
</span><span class="comment">*</span><span class="comment">          = 'N':  Compute eigenvalues only.
</span><span class="comment">*</span><span class="comment">          = 'I':  Compute eigenvectors of tridiagonal matrix also.
</span><span class="comment">*</span><span class="comment">          = 'V':  Compute eigenvectors of original dense symmetric
</span><span class="comment">*</span><span class="comment">                  matrix also.  On entry, Z contains the orthogonal
</span><span class="comment">*</span><span class="comment">                  matrix used to reduce the original matrix to
</span><span class="comment">*</span><span class="comment">                  tridiagonal form.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  N       (input) INTEGER
</span><span class="comment">*</span><span class="comment">          The dimension of the symmetric tridiagonal matrix.  N &gt;= 0.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  D       (input/output) DOUBLE PRECISION array, dimension (N)
</span><span class="comment">*</span><span class="comment">          On entry, the diagonal elements of the tridiagonal matrix.
</span><span class="comment">*</span><span class="comment">          On exit, if INFO = 0, the eigenvalues in ascending order.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  E       (input/output) DOUBLE PRECISION array, dimension (N-1)
</span><span class="comment">*</span><span class="comment">          On entry, the subdiagonal elements of the tridiagonal matrix.
</span><span class="comment">*</span><span class="comment">          On exit, E has been destroyed.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Z       (input/output) DOUBLE PRECISION array, dimension (LDZ,N)
</span><span class="comment">*</span><span class="comment">          On entry, if COMPZ = 'V', then Z contains the orthogonal
</span><span class="comment">*</span><span class="comment">          matrix used in the reduction to tridiagonal form.
</span><span class="comment">*</span><span class="comment">          On exit, if INFO = 0, then if COMPZ = 'V', Z contains the
</span><span class="comment">*</span><span class="comment">          orthonormal eigenvectors of the original symmetric matrix,
</span><span class="comment">*</span><span class="comment">          and if COMPZ = 'I', Z contains the orthonormal eigenvectors
</span><span class="comment">*</span><span class="comment">          of the symmetric tridiagonal matrix.
</span><span class="comment">*</span><span class="comment">          If  COMPZ = 'N', then Z is not referenced.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  LDZ     (input) INTEGER
</span><span class="comment">*</span><span class="comment">          The leading dimension of the array Z.  LDZ &gt;= 1.
</span><span class="comment">*</span><span class="comment">          If eigenvectors are desired, then LDZ &gt;= max(1,N).
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  WORK    (workspace/output) DOUBLE PRECISION array,
</span><span class="comment">*</span><span class="comment">                                         dimension (LWORK)
</span><span class="comment">*</span><span class="comment">          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  LWORK   (input) INTEGER
</span><span class="comment">*</span><span class="comment">          The dimension of the array WORK.
</span><span class="comment">*</span><span class="comment">          If COMPZ = 'N' or N &lt;= 1 then LWORK must be at least 1.
</span><span class="comment">*</span><span class="comment">          If COMPZ = 'V' and N &gt; 1 then LWORK must be at least
</span><span class="comment">*</span><span class="comment">                         ( 1 + 3*N + 2*N*lg N + 3*N**2 ),
</span><span class="comment">*</span><span class="comment">                         where lg( N ) = smallest integer k such
</span><span class="comment">*</span><span class="comment">                         that 2**k &gt;= N.
</span><span class="comment">*</span><span class="comment">          If COMPZ = 'I' and N &gt; 1 then LWORK must be at least
</span><span class="comment">*</span><span class="comment">                         ( 1 + 4*N + N**2 ).
</span><span class="comment">*</span><span class="comment">          Note that for COMPZ = 'I' or 'V', then if N is less than or
</span><span class="comment">*</span><span class="comment">          equal to the minimum divide size, usually 25, then LWORK need
</span><span class="comment">*</span><span class="comment">          only be max(1,2*(N-1)).
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">          If LWORK = -1, then a workspace query is assumed; the routine
</span><span class="comment">*</span><span class="comment">          only calculates the optimal size of the WORK array, returns
</span><span class="comment">*</span><span class="comment">          this value as the first entry of the WORK array, and no error
</span><span class="comment">*</span><span class="comment">          message related to LWORK is issued by <a name="XERBLA.88"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  IWORK   (workspace/output) INTEGER array, dimension (MAX(1,LIWORK))
</span><span class="comment">*</span><span class="comment">          On exit, if INFO = 0, IWORK(1) returns the optimal LIWORK.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  LIWORK  (input) INTEGER
</span><span class="comment">*</span><span class="comment">          The dimension of the array IWORK.
</span><span class="comment">*</span><span class="comment">          If COMPZ = 'N' or N &lt;= 1 then LIWORK must be at least 1.
</span><span class="comment">*</span><span class="comment">          If COMPZ = 'V' and N &gt; 1 then LIWORK must be at least
</span><span class="comment">*</span><span class="comment">                         ( 6 + 6*N + 5*N*lg N ).
</span><span class="comment">*</span><span class="comment">          If COMPZ = 'I' and N &gt; 1 then LIWORK must be at least
</span><span class="comment">*</span><span class="comment">                         ( 3 + 5*N ).
</span><span class="comment">*</span><span class="comment">          Note that for COMPZ = 'I' or 'V', then if N is less than or
</span><span class="comment">*</span><span class="comment">          equal to the minimum divide size, usually 25, then LIWORK
</span><span class="comment">*</span><span class="comment">          need only be 1.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">          If LIWORK = -1, then a workspace query is assumed; the
</span><span class="comment">*</span><span class="comment">          routine only calculates the optimal size of the IWORK array,
</span><span class="comment">*</span><span class="comment">          returns this value as the first entry of the IWORK array, and
</span><span class="comment">*</span><span class="comment">          no error message related to LIWORK is issued by <a name="XERBLA.107"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  INFO    (output) INTEGER
</span><span class="comment">*</span><span class="comment">          = 0:  successful exit.
</span><span class="comment">*</span><span class="comment">          &lt; 0:  if INFO = -i, the i-th argument had an illegal value.
</span><span class="comment">*</span><span class="comment">          &gt; 0:  The algorithm failed to compute an eigenvalue while
</span><span class="comment">*</span><span class="comment">                working on the submatrix lying in rows and columns
</span><span class="comment">*</span><span class="comment">                INFO/(N+1) through mod(INFO,N+1).
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Further Details
</span><span class="comment">*</span><span class="comment">  ===============
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Based on contributions by
</span><span class="comment">*</span><span class="comment">     Jeff Rutter, Computer Science Division, University of California
</span><span class="comment">*</span><span class="comment">     at Berkeley, USA
</span><span class="comment">*</span><span class="comment">  Modified by Francoise Tisseur, University of Tennessee.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  =====================================================================
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     .. Parameters ..
</span>      DOUBLE PRECISION   ZERO, ONE, TWO
      PARAMETER          ( ZERO = 0.0D0, ONE = 1.0D0, TWO = 2.0D0 )
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Local Scalars ..
</span>      LOGICAL            LQUERY
      INTEGER            FINISH, I, ICOMPZ, II, J, K, LGN, LIWMIN,
     $                   LWMIN, M, SMLSIZ, START, STOREZ, STRTRW
      DOUBLE PRECISION   EPS, ORGNRM, P, TINY
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Functions ..
</span>      LOGICAL            <a name="LSAME.137"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
      INTEGER            <a name="ILAENV.138"></a><a href="ilaenv.f.html#ILAENV.1">ILAENV</a>
      DOUBLE PRECISION   <a name="DLAMCH.139"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>, <a name="DLANST.139"></a><a href="dlanst.f.html#DLANST.1">DLANST</a>
      EXTERNAL           <a name="LSAME.140"></a><a href="lsame.f.html#LSAME.1">LSAME</a>, <a name="ILAENV.140"></a><a href="ilaenv.f.html#ILAENV.1">ILAENV</a>, <a name="DLAMCH.140"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>, <a name="DLANST.140"></a><a href="dlanst.f.html#DLANST.1">DLANST</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           DGEMM, <a name="DLACPY.143"></a><a href="dlacpy.f.html#DLACPY.1">DLACPY</a>, <a name="DLAED0.143"></a><a href="dlaed0.f.html#DLAED0.1">DLAED0</a>, <a name="DLASCL.143"></a><a href="dlascl.f.html#DLASCL.1">DLASCL</a>, <a name="DLASET.143"></a><a href="dlaset.f.html#DLASET.1">DLASET</a>, <a name="DLASRT.143"></a><a href="dlasrt.f.html#DLASRT.1">DLASRT</a>,
     $                   <a name="DSTEQR.144"></a><a href="dsteqr.f.html#DSTEQR.1">DSTEQR</a>, <a name="DSTERF.144"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>, DSWAP, <a name="XERBLA.144"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Intrinsic Functions ..
</span>      INTRINSIC          ABS, DBLE, INT, LOG, MAX, MOD, SQRT
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Executable Statements ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Test the input parameters.
</span><span class="comment">*</span><span class="comment">
</span>      INFO = 0
      LQUERY = ( LWORK.EQ.-1 .OR. LIWORK.EQ.-1 )
<span class="comment">*</span><span class="comment">
</span>      IF( <a name="LSAME.156"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( COMPZ, <span class="string">'N'</span> ) ) THEN
         ICOMPZ = 0
      ELSE IF( <a name="LSAME.158"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( COMPZ, <span class="string">'V'</span> ) ) THEN
         ICOMPZ = 1
      ELSE IF( <a name="LSAME.160"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( COMPZ, <span class="string">'I'</span> ) ) THEN
         ICOMPZ = 2
      ELSE
         ICOMPZ = -1
      END IF
      IF( ICOMPZ.LT.0 ) THEN
         INFO = -1
      ELSE IF( N.LT.0 ) THEN
         INFO = -2
      ELSE IF( ( LDZ.LT.1 ) .OR.
     $         ( ICOMPZ.GT.0 .AND. LDZ.LT.MAX( 1, N ) ) ) THEN
         INFO = -6
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.EQ.0 ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Compute the workspace requirements
</span><span class="comment">*</span><span class="comment">
</span>         SMLSIZ = <a name="ILAENV.178"></a><a href="ilaenv.f.html#ILAENV.1">ILAENV</a>( 9, <span class="string">'<a name="DSTEDC.178"></a><a href="dstedc.f.html#DSTEDC.1">DSTEDC</a>'</span>, <span class="string">' '</span>, 0, 0, 0, 0 )
         IF( N.LE.1 .OR. ICOMPZ.EQ.0 ) THEN
            LIWMIN = 1
            LWMIN = 1
         ELSE IF( N.LE.SMLSIZ ) THEN
            LIWMIN = 1
            LWMIN = 2*( N - 1 )
         ELSE
            LGN = INT( LOG( DBLE( N ) )/LOG( TWO ) )
            IF( 2**LGN.LT.N )
     $         LGN = LGN + 1
            IF( 2**LGN.LT.N )
     $         LGN = LGN + 1
            IF( ICOMPZ.EQ.1 ) THEN
               LWMIN = 1 + 3*N + 2*N*LGN + 3*N**2
               LIWMIN = 6 + 6*N + 5*N*LGN
            ELSE IF( ICOMPZ.EQ.2 ) THEN
               LWMIN = 1 + 4*N + N**2
               LIWMIN = 3 + 5*N
            END IF
         END IF
         WORK( 1 ) = LWMIN
         IWORK( 1 ) = LIWMIN
<span class="comment">*</span><span class="comment">
</span>         IF( LWORK.LT.LWMIN .AND. .NOT. LQUERY ) THEN
            INFO = -8
         ELSE IF( LIWORK.LT.LIWMIN .AND. .NOT. LQUERY ) THEN
            INFO = -10
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.210"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="DSTEDC.210"></a><a href="dstedc.f.html#DSTEDC.1">DSTEDC</a>'</span>, -INFO )
         RETURN
      ELSE IF (LQUERY) THEN
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Quick return if possible
</span><span class="comment">*</span><span class="comment">
</span>      IF( N.EQ.0 )
     $   RETURN
      IF( N.EQ.1 ) THEN
         IF( ICOMPZ.NE.0 )
     $      Z( 1, 1 ) = ONE
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     If the following conditional clause is removed, then the routine
</span><span class="comment">*</span><span class="comment">     will use the Divide and Conquer routine to compute only the
</span><span class="comment">*</span><span class="comment">     eigenvalues, which requires (3N + 3N**2) real workspace and
</span><span class="comment">*</span><span class="comment">     (2 + 5N + 2N lg(N)) integer workspace.
</span><span class="comment">*</span><span class="comment">     Since on many architectures <a name="DSTERF.230"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a> is much faster than any other
</span><span class="comment">*</span><span class="comment">     algorithm for finding eigenvalues only, it is used here
</span><span class="comment">*</span><span class="comment">     as the default. If the conditional clause is removed, then
</span><span class="comment">*</span><span class="comment">     information on the size of workspace needs to be changed.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     If COMPZ = 'N', use <a name="DSTERF.235"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a> to compute the eigenvalues.
</span><span class="comment">*</span><span class="comment">
</span>      IF( ICOMPZ.EQ.0 ) THEN
         CALL <a name="DSTERF.238"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>( N, D, E, INFO )
         GO TO 50
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     If N is smaller than the minimum divide size (SMLSIZ+1), then
</span><span class="comment">*</span><span class="comment">     solve the problem with another solver.
</span><span class="comment">*</span><span class="comment">
</span>      IF( N.LE.SMLSIZ ) THEN
<span class="comment">*</span><span class="comment">
</span>         CALL <a name="DSTEQR.247"></a><a href="dsteqr.f.html#DSTEQR.1">DSTEQR</a>( COMPZ, N, D, E, Z, LDZ, WORK, INFO )
<span class="comment">*</span><span class="comment">
</span>      ELSE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        If COMPZ = 'V', the Z matrix must be stored elsewhere for later
</span><span class="comment">*</span><span class="comment">        use.
</span><span class="comment">*</span><span class="comment">
</span>         IF( ICOMPZ.EQ.1 ) THEN
            STOREZ = 1 + N*N
         ELSE
            STOREZ = 1
         END IF
<span class="comment">*</span><span class="comment">
</span>         IF( ICOMPZ.EQ.2 ) THEN
            CALL <a name="DLASET.261"></a><a href="dlaset.f.html#DLASET.1">DLASET</a>( <span class="string">'Full'</span>, N, N, ZERO, ONE, Z, LDZ )
         END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Scale.
</span><span class="comment">*</span><span class="comment">
</span>         ORGNRM = <a name="DLANST.266"></a><a href="dlanst.f.html#DLANST.1">DLANST</a>( <span class="string">'M'</span>, N, D, E )
         IF( ORGNRM.EQ.ZERO )
     $      GO TO 50
<span class="comment">*</span><span class="comment">
</span>         EPS = <a name="DLAMCH.270"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'Epsilon'</span> )
<span class="comment">*</span><span class="comment">
</span>         START = 1
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        while ( START &lt;= N )
</span><span class="comment">*</span><span class="comment">
</span>   10    CONTINUE
         IF( START.LE.N ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           Let FINISH be the position of the next subdiagonal entry
</span><span class="comment">*</span><span class="comment">           such that E( FINISH ) &lt;= TINY or FINISH = N if no such
</span><span class="comment">*</span><span class="comment">           subdiagonal exists.  The matrix identified by the elements
</span><span class="comment">*</span><span class="comment">           between START and FINISH constitutes an independent
</span><span class="comment">*</span><span class="comment">           sub-problem.
</span><span class="comment">*</span><span class="comment">
</span>            FINISH = START
   20       CONTINUE
            IF( FINISH.LT.N ) THEN
               TINY = EPS*SQRT( ABS( D( FINISH ) ) )*
     $                    SQRT( ABS( D( FINISH+1 ) ) )
               IF( ABS( E( FINISH ) ).GT.TINY ) THEN
                  FINISH = FINISH + 1
                  GO TO 20
               END IF
            END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           (Sub) Problem determined.  Compute its size and solve it.
</span><span class="comment">*</span><span class="comment">
</span>            M = FINISH - START + 1
            IF( M.EQ.1 ) THEN
               START = FINISH + 1
               GO TO 10
            END IF
            IF( M.GT.SMLSIZ ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">              Scale.
</span><span class="comment">*</span><span class="comment">
</span>               ORGNRM = <a name="DLANST.307"></a><a href="dlanst.f.html#DLANST.1">DLANST</a>( <span class="string">'M'</span>, M, D( START ), E( START ) )
               CALL <a name="DLASCL.308"></a><a href="dlascl.f.html#DLASCL.1">DLASCL</a>( <span class="string">'G'</span>, 0, 0, ORGNRM, ONE, M, 1, D( START ), M,
     $                      INFO )
               CALL <a name="DLASCL.310"></a><a href="dlascl.f.html#DLASCL.1">DLASCL</a>( <span class="string">'G'</span>, 0, 0, ORGNRM, ONE, M-1, 1, E( START ),
     $                      M-1, INFO )
<span class="comment">*</span><span class="comment">
</span>               IF( ICOMPZ.EQ.1 ) THEN
                  STRTRW = 1
               ELSE
                  STRTRW = START
               END IF
               CALL <a name="DLAED0.318"></a><a href="dlaed0.f.html#DLAED0.1">DLAED0</a>( ICOMPZ, N, M, D( START ), E( START ),
     $                      Z( STRTRW, START ), LDZ, WORK( 1 ), N,
     $                      WORK( STOREZ ), IWORK, INFO )
               IF( INFO.NE.0 ) THEN
                  INFO = ( INFO / ( M+1 )+START-1 )*( N+1 ) +
     $                   MOD( INFO, ( M+1 ) ) + START - 1
                  GO TO 50
               END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">              Scale back.
</span><span class="comment">*</span><span class="comment">
</span>               CALL <a name="DLASCL.329"></a><a href="dlascl.f.html#DLASCL.1">DLASCL</a>( <span class="string">'G'</span>, 0, 0, ONE, ORGNRM, M, 1, D( START ), M,
     $                      INFO )
<span class="comment">*</span><span class="comment">
</span>            ELSE
               IF( ICOMPZ.EQ.1 ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">                 Since QR won't update a Z matrix which is larger than
</span><span class="comment">*</span><span class="comment">                 the length of D, we must solve the sub-problem in a
</span><span class="comment">*</span><span class="comment">                 workspace and then multiply back into Z.
</span><span class="comment">*</span><span class="comment">
</span>                  CALL <a name="DSTEQR.339"></a><a href="dsteqr.f.html#DSTEQR.1">DSTEQR</a>( <span class="string">'I'</span>, M, D( START ), E( START ), WORK, M,
     $                         WORK( M*M+1 ), INFO )
                  CALL <a name="DLACPY.341"></a><a href="dlacpy.f.html#DLACPY.1">DLACPY</a>( <span class="string">'A'</span>, N, M, Z( 1, START ), LDZ,
     $                         WORK( STOREZ ), N )
                  CALL DGEMM( <span class="string">'N'</span>, <span class="string">'N'</span>, N, M, M, ONE,
     $                        WORK( STOREZ ), N, WORK, M, ZERO,
     $                        Z( 1, START ), LDZ )
               ELSE IF( ICOMPZ.EQ.2 ) THEN
                  CALL <a name="DSTEQR.347"></a><a href="dsteqr.f.html#DSTEQR.1">DSTEQR</a>( <span class="string">'I'</span>, M, D( START ), E( START ),
     $                         Z( START, START ), LDZ, WORK, INFO )
               ELSE
                  CALL <a name="DSTERF.350"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>( M, D( START ), E( START ), INFO )
               END IF
               IF( INFO.NE.0 ) THEN
                  INFO = START*( N+1 ) + FINISH
                  GO TO 50
               END IF
            END IF
<span class="comment">*</span><span class="comment">
</span>            START = FINISH + 1
            GO TO 10
         END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        endwhile
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        If the problem split any number of times, then the eigenvalues
</span><span class="comment">*</span><span class="comment">        will not be properly ordered.  Here we permute the eigenvalues
</span><span class="comment">*</span><span class="comment">        (and the associated eigenvectors) into ascending order.
</span><span class="comment">*</span><span class="comment">
</span>         IF( M.NE.N ) THEN
            IF( ICOMPZ.EQ.0 ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">              Use Quick Sort
</span><span class="comment">*</span><span class="comment">
</span>               CALL <a name="DLASRT.373"></a><a href="dlasrt.f.html#DLASRT.1">DLASRT</a>( <span class="string">'I'</span>, N, D, INFO )
<span class="comment">*</span><span class="comment">
</span>            ELSE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">              Use Selection Sort to minimize swaps of eigenvectors
</span><span class="comment">*</span><span class="comment">
</span>               DO 40 II = 2, N
                  I = II - 1
                  K = I
                  P = D( I )
                  DO 30 J = II, N
                     IF( D( J ).LT.P ) THEN
                        K = J
                        P = D( J )
                     END IF
   30             CONTINUE
                  IF( K.NE.I ) THEN
                     D( K ) = D( I )
                     D( I ) = P
                     CALL DSWAP( N, Z( 1, I ), 1, Z( 1, K ), 1 )
                  END IF
   40          CONTINUE
            END IF
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span>   50 CONTINUE
      WORK( 1 ) = LWMIN
      IWORK( 1 ) = LIWMIN
<span class="comment">*</span><span class="comment">
</span>      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="DSTEDC.405"></a><a href="dstedc.f.html#DSTEDC.1">DSTEDC</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

</pre>

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